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能源短缺和环境恶化是人类社会面临的共同挑战.由于资源丰富、环境友好和零碳排放,核聚变能源是未来的理想能源.上世纪90年代以来,磁约束核聚变研究取得重大进展,以建造国际热核实验反应堆(ITER)为标志,聚变能源开发进入工程实施阶段,如果ITER计划取得预期成果,有望在本世纪中叶实现核聚变能源商用化. 相似文献
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能源短缺和环境恶化是人类社会面临的共同挑战.由于资源丰富、环境友好和零碳排放,核聚变能源是未来的理想能源.上世纪90年代以来,磁约束核聚变研究取得重大进展,以建造国际热核实验反应堆(ITER)为标志,聚变能源开发进入工程实施阶段,如果ITER计划取得预期成果,有望在本世纪中叶实现核聚变能源商用化. 相似文献
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Salvatore Iavarone Arthur Péquin Zhi X. Chen Nguyen Anh Khoa Doan Nedunchezhian Swaminathan Alessandro Parente 《Proceedings of the Combustion Institute》2021,38(4):5403-5414
Moderate or Intense Low-oxygen Dilution (MILD) combustion has drawn increasing attention as it allows to avoid the thermo-chemical conditions prone to the formation of pollutant species while ensuring high energy efficiency and fuel flexibility. MILD combustion is characterized by a strong competition between turbulent mixing and chemical kinetics so that turbulence-chemistry interactions are naturally strengthened and unsteady phenomena such as local extinction and re-ignition may occur. The underlying physical mechanisms are not fully understood yet and the validation of combustion models featuring enhanced predictive capabilities is required. Within this context, high-fidelity data from Direct Numerical Simulation (DNS) represent a great opportunity for the assessment and the validation of combustion closure formulations. In this study, the performance of the Partially Stirred Reactor (PaSR) combustion model in MILD conditions is a priori assessed on Direct Numerical Simulations (DNS) of turbulent combustion of MILD mixtures in a cubical domain. Modeled quantities of interest, such as heat release rate and reaction rates of major and minor species, are compared to the corresponding filtered quantities extracted from the DNS. Different submodels for the key model parameters, i.e., the chemical time scale τc and the mixing time scale τmix, are considered and their influence on the results is evaluated. The results show that the mixing time scale is the leading scale in the investigated cases. The best agreement with the DNS data regarding the prediction of heat release rate and chemical source terms is achieved by the PaSR model that employs a local dynamic approach for the estimation of the mixing time scale. An overestimation of the OH species source terms occurs in limited zones of the computational domain, characterized by low heat release rates. 相似文献
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Michael Rueter Hans Guenter Dosch 《Zeitschrift fur Physik C Particles and Fields》1995,66(1-2):245-252
We calculate the squared gluon field strengths of a heavyq- $\bar q$ -pair in the model of the stochastic vacuum. We observe that with increasing separation a chromoelectric flux tube is built. The properties of the emerging flux tube are investigated. 相似文献
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A. Bac?awski 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(11):1986-1994
The radiation emitted from a high-current wall-stabilized arc operated in helium with some admixture of CO2 has been studied. Intensities of fine structure components for 10 multiplets of neutral oxygen (O I) have been determined applying the emission method. On the basis of measured line intensities relative line strengths within each studied multiplet have been obtained. The results are compared with data resulting from the LS-coupling scheme and with other theoretical as well as experimental results available in literature. 相似文献
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Shinagawa J Kurosaki Y Zhang F Parker C Brown SE Jérome D Christensen JB Bechgaard K 《Physical review letters》2007,98(14):147002
(TMTSF)2ClO4 is a quasi-one-dimensional organic conductor and superconductor with Tc=1.4 K, and one of at least two Bechgaard salts observed to have upper critical fields far exceeding the paramagnetic limit. Nevertheless, the 77Se NMR Knight shift at low fields reveals a decrease in spin susceptibility chi(s) consistent with singlet spin pairing. The field dependence of the spin-lattice relaxation rate at 100 mK exhibits a sharp crossover (or phase transition) at a field Hs approximately 15 kOe, to a regime where chi(s) is close to the normal state value, even though Hc2> Hs. 相似文献
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J.-C. Lasjaunias K. Biljaković D. Starešinić P. Monceau S. Takasaki J. Yamada S.-I. Nakatsuji H. Anzai 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(4):541-550
We report on specific heat measurements of the quasi-one-dimensional organic salt (TMTSF)2AsF6 in its spin density wave state between 75 mK and 7 K. Similarly to (TMTSF)2PF6, we find discontinuities in the lattice contribution at 1.9 K an d 3.5 K ascribed to sub-spin density wave phases. Time-dependent
effects due to dynamics of low-energy excitations in metastable states occur only below 0.2 K which yields an activation energy
for the equilibrium energy relaxation process of 0.34 K, 4-5 times smaller than found for (TMTSF)2PF6. Finally the reduction of the low-energy excitations contribution to the specific heat in comparison to PF6 reveals an intermediate cubic-like regime between 0.25 and 0.5 K that we tentatively describe as the phason contribution
of the incommensurate spin density wave modulation.
Received: 17 March 1998 / Revised: 27 July 1998 / Accepted: 22 September 1998 相似文献
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V. B. Kapustyanyk 《Journal of Applied Spectroscopy》1998,65(3):427-433
Based on the data from optical-spectral studies of (NH2(CH3)2)2CoCl4 crystals, the existence of high-temperature phase transitions at 419, 380, 352, and 313 K is confirmed. It was shown that
with the exception of the first transition, they are related to a considerable extent to rearrangement of the network of hydrogen
bonds and are not accompanied by, considerable deformation of the lattice. In this connection the character of the electron-phonon
interaction remains unchanged in the entire temperature range of the measurements. The (NH2(CH3)2)2CoCl4 structure at room temperature is close to that of the ordered low-temperature phases of such isomorphous crystals as β-K2SO4.
I. Franko State University, L’vov, Ukraine, 8, Kirill and Mefodii St., UA-290005, L’vov. Translated from Zhurnal Prikladnoi
Spektroskopii, Vol. 65, No. 3, pp. 412–418, May–June, 1998. 相似文献
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W. G. Clark G. Wu P. Ranin L. K. Montgomery L. Balicas 《Applied magnetic resonance》2004,27(1-2):279-287
The two-dimensional organic conductor λ-(BETS)2FeCl4 has an unusual phase diagram as a function of temperature and magnetic field that includes a paramagnetic metal (PM) phase, an antiferromagnetic insulating (AFI) phase, and a field-induced superconducting phase (S. Uji, H. Kobayashi, L. Balicas, J. S. Brooks: Adv. Mater. 14: 243, 2002). Here, we report a preliminary investigation of the PM and AFI phases at 9 T over the temperature range of 2.0–180 K that uses proton nuclear magnetic resonance measurements of the spectrum, the spin-lattice relaxation rate 1/T 1, and the spin echo decay rate 1/T 2. The sample is a small single crystal whose mass is about 3 μg (approximately 2·1016 protons). Its small size creates several challenges that include detecting small signals and excluding parasitic proton signals that are not from the sample (H. N. Bachman, I. F. Silvera: J. Magn. Reson. 162: 417, 2003). These strategies and other techniques used to obtain viable signals are described. 相似文献
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Since their discovery in the mid-1990s, ultrafast laser filaments in gases have been described as products of a dynamic balance between Kerr self-focusing and defocusing by free electric charges that are generated via multiphoton ionization on the beam axis. This established paradigm has been recently challenged by a suggestion that the Kerr effect saturates and even changes sign at high intensity of light and that this sign reversal, not free-charge defocusing, is the dominant mechanism responsible for the extended propagation of laser filaments. We report qualitative tests of the new theory based on electrical and optical measurements of plasma density in femtosecond laser filaments. Our results consistently support the established paradigm. 相似文献
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The pressure-temperature phase diagram of the organic Mott insulator kappa-(ET)2Cu2(CN)3, a model system of the spin liquid on triangular lattice, has been investigated by 1H NMR and resistivity measurements. The spin-liquid phase is persistent before the Mott transition to the metal or superconducting phase under pressure. At the Mott transition, the spin fluctuations are rapidly suppressed and the Fermi-liquid features are observed in the temperature dependence of the spin-lattice relaxation rate and resistivity. The characteristic curvature of the Mott boundary in the phase diagram highlights a crucial effect of the spin frustration on the Mott transition. 相似文献
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G. Faraji M. M. Mashhadi K. Abrinia H. S. Kim 《Applied Physics A: Materials Science & Processing》2012,107(4):819-827
Tubular channel angular pressing is a recently developed technique for producing ultrafine grained and nanostructured tubular components. The current study dealt with the influence of the channel angles, friction coefficient and back pressure on the plastic deformation behavior and strain homogeneity in TCAP processing. The FEM results demonstrated that the equivalent plastic strains of 1.65–2.15, 2.15–2.85, and 2.5–3.75 have been achieved after applying one pass TCAP with channel angles of 120°, 90°, and 60°, respectively. Increasing the channel angle leads to lower equivalent plastic strain while obtaining better strain homogeneity. The homogeneity of the strain through the length of the processed tube is very good for all channel angles. Increasing the back pressure leads to slightly higher strain level while the strain homogeneity is decreased. Force results showed that lower loads were required for lower channel angles. It was also observed that for different values of coefficient of friction and channel angles, the load values converged to a constant value at the end of the process. Microstructural observations showed a significant decrease in grain size from the initial value of ~150 μm to about?1?μm. 相似文献
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L.I. Johansson P.M. Stefan M.L. Shek A.N∅rlund Christensen 《Solid State Communications》1980,36(11):965-967
The energy band dispersions of TiN along the Γ-X symmetry line have been determined using a TiN(100) crystal and the angle-resolved photoemission technique combined with tunable synchrotron radiation. Using the direct transition model with a free-electron like final state, the dispersions are mapped out by varying the photon energy. The results are compared to an APW energy band calculation. 相似文献
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Non-destructive testing of tubes using a time reverse numerical simulation (TRNS) method 总被引:4,自引:0,他引:4
A method for the detection of defects in cylindrical structures and the determination of their positions and orientations is presented in this paper. The scattered field, which is generated by the interaction of excited guided waves with a defect, is evaluated with an approach named time reverse numerical simulation method (TRNS). Since the excited waves and the scattered field propagate along the sample, the time-consuming scanning of the whole tube can be eliminated. The scattered displacement field is measured in three dimensions over time with a laser vibrometer at different locations distributed equally around the circumference at a fixed axial coordinate far away from the defect. Instead of analyzing the complicated time signals directly, they are played back in time. If the recorded displacement histories of the scattered field are reversed in time and played back in an identical structure, the waves travel back the same path and interfere to a maximum at their origin. The result is an amplitude increase at the position of the defect where the scattered field was generated. Instead of playing back the recorded time signals in an experiment, this step is replaced by a numerical simulation. Only this enables the visualization and detection of the amplitude increase. As long as the simulation is of high accuracy, the position of the maximum interference corresponds exactly to the location of the defect in the experiment, although no defect is implemented in the simulation. 相似文献